Jessica Chastain had a remarkable year in 2011 — bursting onto the scene with an Oscar-nominated role in The Help — and didn’t slow down in 2012. She tops off a busy year with a Oscar-nominated turn in Zero Dark Thirty, in wide release Jan. 11. She plays Maya, a CIA operative based on a real person, dedicated to following the lead that would eventually guide agents to Osama bin Laden. Maya is professionally unemotional, but that doesn’t mean Chastain didn’t bring strong feelings to the part. The actress spoke to TIME about what she learned along the way.

The making of Zero Dark Thirty was top secret. Was there anything in particular that was really hard to keep secret before the movie was screened?

It’s hard not to talk about the part I was playing. I wanted to scream it from the rooftops that there was a woman that really should be acknowledged and celebrated. The wonderful thing about making this movie is, because she’s an undercover CIA agent who can’t get credit for the wonderful work she did, in a way it’s like thanking her and giving her credit anonymously.

Do you hope she sees the movie?

Yeah. Absolutely.

How did her gender affect her as a character?

I found her to be very similar to Kathryn Bigelow. So many people in the press talk about how Kathryn Bigelow is a female director, and she’s a great director can you believe it! It’s a strange kind of thing that happens. But when you’re on a set, you just go, “What an amazing filmmaker,” and you don’t go, “And she’s a woman.” You never have that thought when working with her. Maya never stops to make a monologue about the glass ceiling she’s facing in the CIA because that deviates from her job.

How did you feel about the fact that she’s referred to as a “girl” despite what she’s doing?

That line at the very end of the movie, where you’ve seen her for close to a decade, the sacrifices she’s made, the servitude of this mission, and she identifies the body and the guy says “100%” — and, for me, I was like, Yes, finally, someone is 100% [sure] like Maya — and then he says “the girl confirmed it.” Right in the moment where you think she’s going to get credit, he doesn’t even use her name. Even at the end of the film after everything she’s accomplished, she’s still referred to as the girl. I don’t think that’s a mistake in the writing, but also I don’t think that’s a mistake in his research. I imagine that when [Mark Boal] was learning about her, she was probably referred to as “the girl.”

Is that something you have personal experience with?

Yeah, actually. This is a very rare lead role in cinema. Women, I find, we’re defined a lot by men and thus defined by our gender, who we are through our relationship with men, be it as a victim or a love relationship. The idea that this is a woman who defines herself by her work and by her brain and doesn’t try to sleep with her superiors, that to me is really inspiring. I’m in a very different business. As an actor, there are a lot of women around. Not as many women as men, but there are more women around than in a field like the CIA. I don’t experience that [numbers difference], but I do experience that in our society we are still labeled by our gender.

It’s so interesting that there’s so little of Maya’s personal life in the movie. Were your ideas about her background just the product of your imagination, or did you discuss it with Kathryn Bigelow and Mark Boal?

There’s little about her personal life because the real woman did not have a personal life. However, I had to create where I came from, and you see little clues in the movie of a personal life, of a shadow of who Maya was before this. You see a screen saver, you see in Islamabad there’s a drawing made by a child hanging in her room, so there are little bits of the personal that have been added that come from my imagination that went along the lines of “this kind of makes sense with who this woman could have been.” I had to know as an actor where am I coming from and where am I going. You can’t end the movie and not know where you started.

How did you balance, in coming up with that backstory, being “the girl” and also being a “killer”?

I love that scene, because they’re talking about “Isn’t she young?” and he says that in D.C. she’s known as the killer. If you take each scene, there are so many clues about who this woman is. She’s known in D.C. She’s recruited right out of high school. All that says she’s never been in an environment like this before, but also it means she’s really good at what she does back home. Is she going to find her way here? It also says she’s younger than they’ve ever really gone before, so why did they send her out? What does she have that makes her a rock star in the field? Every scene in the movie had little clues like that.

I heard you brought prop pictures of terrorists home with you to get in character. Were there other ways in which you brought Maya home during the filming?

I guess the idea of being cut off from friends and family. I didn’t go all method and tell my family, “I’m not going to talk to you guys for six months.” I think that’s a bit extreme for me to do; I don’t imagine ever doing that. But it was a very lonely existence. I’m someone that has a very close relationship with my friends and family, so to be so far away from everyone and to be in that part of the world where if I would go to a restaurant with three actors from the film in a very nice hotel in Amman, Jordan, which is supposed to be pretty liberal, they wouldn’t give me a menu — all of that kind of thing really fed the fire of what Maya was living in. I know when I left, it was like, back in America, what is going on, what do I do now?

What was the biggest source of culture shock when you came back?

What I found is how clean everything is. You know that scene where you first see Maya go into her office and there’s that dust? That was something we just discovered. We were in an area — Chandigarh in India, about three hours from Pakistan by driving — and everything is dusty, no matter what you do. I kept trying to clean the area, and it would get another layer of dust. You can see in the film that we didn’t make this movie in the United States. Even the dust, it changes the lighting.

I was sure I was going to be an actor when I was a kid. At 8 years old I was like, “I’m an actor,” and people go, “O.K., yeah, I used to want to be a ballerina.” It’s like, You’re not listening to me, but I’m right. I did feel that about acting. And I was right!

You’ve said that you spent a long time reading about the war on terror as research. Which book would you recommend most?The Looming Tower. That book is incredible. It’s not just about Osama bin Laden. Everything that led to 9/11. And then what I found to be the most helpful book was Michael Scheuer’s book on Osama bin Laden. There was so much about him that I had no idea of.

Anything particularly surprising?

I was shocked by how generous bin Laden was financially with people. Whenever they needed money, he would give it to them. In the book it talked about him as a child. He would be in a taxi and the driver would be listening to music that he found to be inappropriate for his sister, so he would demand they turn the music off. This is all information Maya would have known about him.

What genre would you say it belongs to?

It’s a complicated one, isn’t it? When I read the script I immediately thought of All the President’s Men — because it’s reporting current events in our society — but then it also affects me like that movie Coming Home with Jane Fonda. I learned so much about vets in the Vietnam War through that film. That was a fictional story, but I feel like this film creates that same kind of look at us as a society.